Tricam axial extension to provide gripping tool with improved operational range and capacity

ABSTRACT

An improvement in a gripping tool having a grip surface carried by movable grip elements and cam linkages to radially move the grip surface from a retracted to an extended position. The improvement involves a tri-cam linkage with cam pairs supporting bi-rotary to axial stroke activation and further cam linkages to cause radial stroke of the tool grip surface as a function of axial stroke.

FIELD OF THE INVENTION

This invention relates intentionally to applications where tubulars and tubular strings must be gripped, handled and hoisted with a tool connected to a drive head or reaction frame to enable the transfer of both axial and torsional loads into or from the tubular segment being gripped. In the field of earth drilling, well construction and well servicing with drilling and service rigs this invention relates to slips, and more to specifically, on rigs employing top drives, applies to tubular running tools that attach to the top drive for gripping the proximal segment of tubular strings being assembled into, deployed in or removed from the well bore. Such tubular running tools support various functions necessary or beneficial to these operations including rapid engagement and release, hoisting, pushing, rotating and flow of pressurized fluid into and out of the tubular string. This invention provides linkages to extend or improve the gripping range of such tubular running tools.

BACKGROUND OF THE INVENTION

Until recently, power tongs were the established method used to run casing or tubing strings into or out of petroleum wells, in coordination with the drilling rig hoisting system. This power tong method allows such tubular strings, comprised of pipe segments or joints with mating threaded ends, to be relatively efficiently assembled by screwing together the mated threaded ends (make-up) to form threaded connections between sequential pipe segments as they are added to the string being installed in the well bore; or conversely removed and disassembled (break-out). But this power tong method does not simultaneously support other beneficial functions such as rotating, pushing or fluid filling, after a pipe segment is added to or removed from the string, and while the string is being lowered or raised in the well bore. Running tubulars with tongs also typically requires personnel deployment in relatively higher hazard locations such as on the rig floor or more significantly, above the rig floor, on the so called ‘stabbing boards’.

The advent of drilling rigs equipped with top drives has enabled a new method of running tubulars, and in particular casing, where the top drive is equipped with a so called ‘top drive tubular running tool’ to grip and perhaps seal between the proximal pipe segment and top drive quill. (It should be understood here that the term top drive quill is generally meant to include such drive string components as may be attached thereto, the distal end thereof effectively acting as an extension of the quill.) Various devices to generally accomplish this purpose of ‘top drive casing running’ have therefore been developed. Using these devices in coordination with the top drive allows hoisting, rotating, pushing and filling of the casing string with drilling fluid while running, thus removing the limitations associated with power tongs. Simultaneously, automation of the gripping mechanism combined with the inherent advantages of the top drive reduces the level of human involvement required with power tong running processes and thus improves safety.

In addition, to handle and run casing with such top drive tubular running tools, the string weight must be transferred from the top drive to a support device when the proximal or active pipe segments are being added or removed from the otherwise assembled string. This function is typically provided by an ‘annular wedge grip’ axial load activated gripping device that uses ‘slips’ or jaws placed in a hollow ‘slip bowl’ through which the casing is run, where the slip bowl has a frusto-conical bore with downward decreasing diameter and is supported in or on the rig floor. The slips then acting as annular wedges between the pipe segment at the proximal end of the string and the frusto-conical interior surface of the slip bowl, tractionally grip the pipe but slide or slip downward and thus radially inward on the interior surface of the slip bowl as string weight is transferred to the grip. The radial force between the slips and pipe body is thus axial load self-activated or ‘self-energized’, i.e., considering tractional capacity the dependent and string weight the independent variable, a positive feedback loop exists where the independent variable of string weight is positively fed back to control radial grip force which monotonically acts to control tractional capacity or resistance to sliding, the dependent variable. Similarly, make-up and break-out torque applied to the active pipe segment must also be reacted out of the proximal end of the assembled string. This function is typically provided by tongs which have grips that engage the proximal pipe segment and an arm attached by a link such as a chain or cable to the rig structure to prevent rotation and thereby react torque not otherwise reacted by the slips in the slip bowl. The grip force of such tongs is similarly typically self-activated or ‘self-energized’ by positive feed back from applied torque load.

In general terms, the gripping tool of PCT patent application CA 2006/00710 and U.S. national phase application Ser. No. 11/912,665, may be summarized as a gripping tool which includes a body assembly, having a load adaptor coupled for axial load transfer to the remainder of the body, or more briefly the main body, the load adaptor adapted to be structurally connected to one of a drive head or reaction frame, a gripping assembly carried by the main body and having a grip surface, which gripping assembly is provided with activating means to radially stroke or move from a retracted position to an engaged position to radially tractionally engage the grip surface with either an interior surface or exterior surface of a work piece in response to relative axial movement or axial stroke of the main body in at least one direction, relative to the grip surface. A linkage is provided acting between the body assembly and the gripping assembly which, upon relative rotation in at least one direction of the load adaptor relative to the grip surface, results in relative axial displacement of the main body with respect to the gripping assembly to move the gripping assembly from the retracted to the engaged position in accordance with the action of the activating means.

This gripping tool thus utilizes a mechanically activated grip mechanism that generates its gripping force in response to axial load or axial stroke activation of the grip assembly, which activation occurs either together with or independently from, externally applied axial load and externally applied torsion load, in the form of applied right or left hand torque, which loads are carried across the tool from the load adaptor of the body assembly to the grip surface of the gripping assembly, in tractional engagement with the work piece.

It will be apparent that the utility of this or other similar gripping tools is a function of the range of work piece sizes, typically expressed as minimum and maximum diameters for tubular work pieces, which can be accommodated between the fully retracted and fully extended grip surface positions of a given gripping tool, i.e., the radial size and radial stroke of the gripping surface. The utility of a given gripping tool can be improved if it can accommodate a greater range of work pieces sizes. The present invention is directed toward meeting this need in applications where greater radial size and radial stroke are beneficial such as often occurs when adapting gripping tools for running oilfield tubulars.

SUMMARY OF THE INVENTION

In accordance with a broad aspect of the present invention, extension linkages are provided for use with a gripping tool in support of extending the radial stroke and work piece sizes that can be accommodated by a given gripping tool that has a grip surface carried by movable grip elements. This involves a tri-cam linkage with cam pairs supporting bi-rotary to axial stroke activation and further cam linkages to cause radial to stroke of the tool grip surface as a function of axial stroke.

The tri-cam linkage includes:

-   -   a drive cam body,     -   an intermediate cam body,     -   a driven cam body,     -   a drive cam pair acting between the drive cam body and         intermediate cam body, and     -   a driven cam pair acting between the intermediate cam body and         driven cam body.

It is preferred that the drive cam pair be arranged to only be active to cause axial stroke as a function of rotation under a first direction of rotation and the driven cam pair under the second direction of rotation which separation of bi-rotary activation into two cam pairs facilitates providing greater axial stroke and correlatively radial stroke of the grip surface than is possible where a single cam pair is employed in a bi-rotary activated linkage.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein:

FIG. 1 is a partial cutaway trimetric view of a simplified version of a bi-axial bi-rotary activated external grip tubular running tool, provided with single cam pair base configuration cam architecture, shown as it would appear with application of right hand torque.

FIG. 2A is a schematic of the single cam pair base configuration cam architecture shown in FIG. 1 in a two dimensional representation, shown as it would appear with application of right hand torque.

FIG. 2B is a schematic of the cam architecture of FIG. 2A in a two dimensional representation, shown as it would appear with application of left hand torque.

FIG. 3 is a schematic of a tri-cam architecture in a two dimensional representation, shown as it would appear with no applied torque.

FIG. 4A is a schematic of the tri-cam architecture of FIG. 3 in a two dimensional representation, shown as it would appear with application of right hand torque.

FIG. 4B is a schematic of the tri-cam architecture of FIG. 3 in a two dimensional representation, shown as it would appear with application of left hand torque.

FIG. 4C is a schematic of the tri-cam architecture of FIG. 3 in a two dimensional representation, shown as it would appear in a gripping tool with axial tension applied.

FIG. 5A is a schematic of a tri-cam architecture with dog boost cam pair in a two dimensional representation, shown as it would appear with application of left hand torque.

FIG. 5B is a schematic of the tri-cam architecture of FIG. 5A with dog boost cam pair in a two dimensional representation, shown as it would appear with a small amount of right hand rotation prior to dog boost in the neutral position.

FIG. 5C is a schematic of the tri-cam architecture of FIG. 5A with dog boost cam pair in a two dimensional representation, shown as it would appear with application of right hand torque.

FIG. 6A is a schematic of the tri-cam architecture of FIG. 3 with latch in a two dimensional representation, shown as it would appear in the latched position.

FIG. 6B is a schematic of the tri-cam architecture of FIG. 3 with latch in a two dimensional representation, shown as it would appear with right hand torque applied with latch disengaged.

FIG. 6C is a schematic of the tri-cam architecture of FIG. 3 with latch in a two to dimensional representation, shown as it would appear with latch disengaged and left hand torque applied.

FIG. 7A is a schematic of the tri-cam architecture of FIG. 3 with a lockout capable latch in a two dimensional representation, shown as it would appear in the latched position.

FIG. 7B is a schematic of the tri-cam architecture of FIG. 3 with a lockout capable latch in a two dimensional representation, shown as it would appear with right hand torque applied with latch disengaged.

FIG. 7C is a schematic of the tri-cam architecture of FIG. 3 with a lockout capable latch in a two dimensional representation, shown as it would appear with latch disengaged and left hand torque applied.

FIG. 7D is a schematic of the tri-cam architecture of FIG. 3 with a lockout capable latch in a two dimensional representation, shown as it would appear with latch disengaged and compression applied from engagement on the driven cam pair.

FIG. 7E is a schematic of the tri-cam architecture of FIG. 3 with a lockout capable latch in a two dimensional representation, shown as it would appear with latch disengaged and compression applied from engagement on the drive cam pair.

FIG. 7F is a schematic of the tri-cam architecture of FIG. 3 with a lockout capable latch in a two dimensional representation, shown as it would appear with the latch locked out and right hand torque applied.

FIG. 8 is an external view of a tubular running tool with tri-cam architecture shown as it would appear in the latched position.

FIG. 9 is a cross section view of a tubular running tool with tri-cam architecture shown as it would appear in the latched position located internal to proximal end of a work piece.

FIG. 10A is an external view of a tri-cam assembly shown as it would appear in the latched position.

FIG. 10B is a cross section view of a tri-cam assembly shown as it would appear in the latched position.

FIG. 11A is an external view of a partial latch assembly including drive cam body, latch ring and latch keys, shown as it would appear in the latched position.

FIG. 11B is a trimetric partial section view of a partial latch assembly including driven cam body, latch ring and latch keys, shown as it would appear disengaged.

FIG. 11C is an external view of a partial latch assembly including drive cam body, latch ring and latch keys, shown as it would appear disengaged.

FIG. 12A is an external view of a tri-cam assembly, shown as it would appear with right hand torque applied.

FIG. 12B is a cross section view of tri-cam assembly, shown as it would appear with right hand torque applied.

FIG. 13A is an external view of a tri-cam assembly, shown as it would appear with latch disengaged and left hand torque applied.

FIG. 13B is a cross section view of tri-cam assembly, shown as it would appear with latch disengaged and left hand torque applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS General Principles

The gripping tool described in PCT patent application CA 2006/00710, is comprised of three main interacting components or assemblies: 1) a body assembly, 2) a gripping assembly carried by the body assembly, and 3) a linkage acting between the body assembly and gripping assembly. The body assembly generally provides structural association of the tool components and includes a load adaptor by which load from a drive head or reaction frame is transferred into or out of the remainder of the body assembly or the main body. The gripping assembly, has a grip surface, is carried by the main body of the body assembly and is provided with means to radially stroke or move the grip surface from a retracted to an engaged position in response to relative axial movement, or axial stroke, to radially and tractionally engage a work piece with the grip surface. The gripping assembly thus acts as an axial load or axial stroke activated grip element.

The main body is coaxially positioned with respect to the work piece to form an annular space in which the axial stroke activated gripping assembly is placed and connected to the main body. The grip surface of the gripping assembly is adapted for conformable, circumferentially distributed and collectively opposed, tractional engagement with the work piece. The means to radially stroke the gripping surface carried by the gripping assembly is configured to link relative axial displacement, or axial stroke, in at least one axial direction, into radial displacement or radial stroke of the grip surface against the work piece with correlative axial and collectively opposed radial forces then arising such that the radial grip force at the grip surface enables reaction of applied axial load and torque into the work piece, where the distributed radial grip force is internally reacted, which arrangement comprises an axial load activated grip mechanism where axial load is carried between the drive head or reaction frame and work piece; the load adaptor, main body and grip element, generally acting in series.

The linkage acting between the body assembly and gripping assembly is adapted to link relative rotation between the load adaptor and grip surface into axial stroke of the gripping assembly and hence radial stroke of the grip surface. The axial load activated grip mechanism is thus arranged to allow relative rotation between one or both of axial load carrying interfaces between the load adaptor and main body or main body and grip element which relative rotation is limited by at least one rotationally activated linkage mechanism which links relative rotation between the load adaptor and grip surface into axial stroke of the grip element and hence radial stroke of the grip surface. The linkage mechanism or mechanisms may be configured to provide this relationship between rotation and axial stroke in numerous ways such as with pivoting linkage arms or rocker bodies acting between the body assembly and gripping assembly but can also be provided in the form of cam pairs acting between the grip element and at least one of the main body or load transfer adaptor to thus readily accommodate and transmit the axial and torsional loads causing, or tending to cause, rotation and to promote the development of the radial grip force. The cam pairs, acting generally in the manner of a cam and cam follower, having contact surfaces are arranged in the preferred embodiment to link their combined relative rotation, in at least one direction, into axial stroke of the grip element in a direction tending to tighten the grip, which axial stroke thus has the same effect as and acts in combination with axial stroke induced by axial load carried by the grip element. Application of relative rotation between the drive head or reaction frame and grip surface in contact with the work piece, in at least one direction, thus causes radial stroke or radial displacement of the grip surface into engagement with the work piece with correlative axial, torque and radial forces then arising such that the radial grip force at the grip surface enables reaction of torque into the work piece, which arrangement comprises torsional load activation so that together with the said axial load activation, the grip mechanism is self-activated in response to bi-axial combined loading in at least one axial and at least one tangential or torsional direction.

Also according to the teaching of PCT patent application CA 2006/00710, cam assemblies may be employed in various arrangements as summarized there in Table 1, where those assemblies providing the function of a “cam” in Table 1 induce relative axial movement between the driving and driven cams as a function of applied relative rotation; which relationship is controlled by the selection of local pitch or helix angle active on the mating cam pair. Where this action must be bi-rotary (include both right and left hand activation) and is provided by a cam assembly comprised of a single cam pair, illustratively shown as saw-tooth profiles between the mating profiled ends of generally cylindrical and co-axially aligned rigid bodies in say FIG. 11B (showing a cam used in the Base or Configuration 1 architecture of Table 1 as it might appear in an external gripping tool), which is reproduced here as FIG. 1, showing cam assembly 1 having a drive cam 2 and driven cam 3 providing single cam pair 4 as they would appear under application of right hand rotation. We here adopt the convention of referring to the “drive” and “driven” cams as a pedagogical convenience to provide a reference for the relative motions and forces described. These are not to be understood as restrictive with respect to application so that in general the cam systems being described can be inverted.

Referring now to FIG. 2A, cam assembly 1 is shown schematically in a two dimensional representation where the axial and tangential directions are shown as ordinate and abscissa respectively in the plot provided with FIG. 2A. Tangential position thus represents circumferential location and tangential displacement represents rotation. Cam pair 4 is represented by mating multi-start right hand helical load surfaces 5, shown here as two starts with an intermediate helical angle, and two to start left hand helical load surfaces 6, shown here with relatively shallow helix angle, i.e., smaller pitch than helical load surfaces 5, where the intersection of helical load surfaces 5 and 6 form cusps or peaks 7. It is apparent that as relative rotation is increased in a right hand direction, left hand helical load surfaces 6 are engaged where the engaged tangential contact length “C” decreases while relative axial separation “Z” (axial stroke) between the driving and driven cams increases until a limiting position is reached where further rotation would result in the peaks riding over each other. Because the cam pair must also transmit load, the limiting position actually occurs when the amount of contact is insufficient to bear the required load allowing a total displacement represented by vector R in the plot shown where the axial component of R equals Z, i.e., axial stroke. Referring now to FIG. 2B, this same limitation is shown for cam assembly 1 as it would appear under application of left hand rotation to drive cam body 2 relative to driven cam body 3 causing right hand helical load surfaces 5 to be active where the total displacement is represented by vector L. There are thus limits to the axial stroke and load capacity (represented by dimensions Z and C respectively in FIGS. 2A and 2B) of such a bi-rotary single cam pair, especially when combined with other competing design variables such as preferred pitch or helix angles governing both left and right hand activation as is apparent by comparing cam pair 4 in FIGS. 2A and 2B under right hand and left hand rotation respectively. While such single cam pair configurations providing axial stroke as a function of imposed relative bi-directional rotation provide substantial utility, in certain applications yet more stroke and load capacity are desirable.

It is one purpose of the present invention to provide means to reduce or effectively remove this limitation in operating range and capacity inherent to bi-directional single cam pairs which means is thus adaptable to any of the linkages referred to as a “cam” in Table 1 of PCT CA 2006/00710. Referring now to FIG. 3, the improved cam architecture of the present invention (again shown in a schematic two dimensional representation where the axial and tangential directions are shown as ordinate and abscissa respectively) provides tri-cam assembly 10, having drive cam body 12, driven cam body 13 and at least one intermediate cam body 14 to act between the drive cam body 12 and driven cam body 13; and is thus referred to herein as a tri-cam architecture. A drive cam pair 15 is provided to act between the drive and intermediate cams, 12 and 14 respectively, and a driven cam pair 16, is provided to act between the intermediate and driven cams, 14 and 13 respectively. Drive cam pair 15 is comprised of mating stop dogs 17 defined by relatively steep helical angle (here shown as vertical) mating dog stop surfaces 18 and relatively shallow left hand helix angle mating helical dog ramp surfaces 19 where the mating helical dog ramp surfaces 19 also act continuous with mating load threads 20. Driven cam pair 16 is comprised of mating load ramps 21 defined by relatively steep helical angle mating ramp stop surfaces 22 (here shown as vertical) and right hand mating helical load ramp surfaces 23, here shown as having an intermediate helix angle (similar to that of right hand helical load surfaces 5 illustrated for cam pair 4 of FIG. 1).

Referring now to FIG. 4A, tri-cam assembly 10 is shown as it would appear under application of some right hand rotation causing relative displacement of drive cam pair 15 initially causing separation of dog stop surfaces 18 and under sufficient rotation also causing separation of dog ramp surfaces 19 so that the load is completely carried by mating load threads 20 at a displacement or over a range indicated by vector R. It will now be apparent that under right hand rotation the axial stroke and load capacity of load cam pair 15 are not limited to the usable contact length of helical dog ramp surfaces 19 but are only limited by load threads 20 which can be readily arranged to provide sufficient engaged length and strength to provide adequate strength with virtually unlimited axial stroke, effectively removing these as limitations for design purposes. In fact, dog ramp surfaces 19 are redundant and need not be engaged at all.

Referring still to FIG. 4A, the helix angles of load ramps 21 and ramp stop surfaces 22 defining driven cam pair 16 are selected with respect to the helix angle of load threads 20, and other variables such as friction coefficient as will be apparent to one skilled in the art, so that under the action of advancing or retracting right hand rotation, no displacement occurs in driven cam pair 16.

Referring now to FIG. 4B, cam assembly 10 is shown as it would appear under application of left hand rotation of drive cam body 12 relative to driven cam body 13. In this case driven cam pair 16 is active and functions in a manner analogous to that already described for drive cam pair 15 with load ramp helix directions reversed. Application of left hand rotation to drive cam body 12 causes ramp stop surfaces 21 to separate and correlatively sliding contact on helical load surfaces 23 causes intermediate cam body 14 and drive cam body 12 to displace axially upward relative to driven cam body 13 providing displacement over a range indicated by vector L. Axial and left hand torque load, carried by tri-cam assembly 10, is reacted through drive cam pair 15 where stop dogs 17, through selection of the helix angle on contacting dog stop surfaces 18 and positioning, can be arranged to control the manner in which load is reacted through drive cam pair 15 to control stress and prevent torsional load from tending to thread lock intermediate cam body 14 to drive cam body 12 in consequence of their coupling through load thread 20, i.e., thread frictional locking in the manner of a nut and bolt. Also, similar to the behaviour under right hand rotation already described, the helix angle of load ramps 21 is selected with respect to the helix angle of load threads 20, so that under the action of advancing or retracting left hand rotation, no displacement occurs in drive cam pair 15.

It will now be apparent that tri-cam assembly 10 provides two cam pairs (drive cam pair 15 and driven cam pair 16): the first active and providing axial stroke under right hand rotation while the second is static; and the second active and providing axial stroke under left hand rotation while the first is static.

Comparing displacement vectors R & L between FIGS. 2A & 2B with 4A and 4B respectively, illustrates that for comparable geometric parameters a greater axial stroke can be achieved under both right and left hand rotation with drive and driven cam pairs 15 and 16 (FIGS. 4A & B) of the tri-cam architecture 10 than can be achieved with a single bi-directional cam pair 4 (FIGS. 2A & B).

Referring again to FIG. 4B, given the above teaching incorporating load threads 20 into the drive cam pair 15, it will now be apparent that load threads can be provided to act in coordination with mating helical load surfaces 23 to increase stroke and load capacity; however in certain applications as can occur with tubular running tools, it is advantageous to allow free separation of the drive and driven cam bodies 12 and 13 respectively, which is allowed by the illustrated configuration shown in FIG. 4C where intermediate cam body 14 remains coupled by load threads 20 to drive cam body 12 but is not so coupled to driven cam body 13 allowing free separation as might be required to ensure grip activation under application of axial load without concurrent rotation when tri-cam assembly 10 is used in say the Base (Configuration 1) architecture of a gripping tool as shown in FIG. 1.

As an intermediate architecture (not shown), where load threads coupling driven cam body 13 and intermediate cam body 14 are desirable, yet some degree of similar freedom for axial separation is also required, the load threads can be provided with substantial backlash. It will be evident to one skilled in the art that for single start threads this backlash is only limited by the thread pitch less the required thread tooth thicknesses so that substantial free axial separation can be achieved for applications where relatively larger pitch can be accommodated, i.e., applications where low helix angle is not required.

As an additional intermediate architecture (not shown), both cam pairs could be arranged as dog ramp surfaces continuous with load threads (with a small backlash), and as such would be referred to as a quad-cam architecture (not shown). The quad-cam architecture would be arranged with a fourth cam component constrained to allow axial movement but not rotational movement relative to the driven cam and rigidly attached to the grip assembly such that on release of the latch, the cam assembly retains the ability to freely stroke axially to engage the work piece under a biasing load. Such an arrangement would be beneficial if a stroke greater than could be accommodated on the tri-cam architecture (specifically limited by the driven cam pair arrangement) was required.

Referring again to FIG. 4B, the summation of axial height and hence strength capacity of stop dogs 17 will be seen to be a function of pitch or helix angle selected for mating load threads 20 (and similarly dog ramp surfaces 19), so that for applications where low thread helix angle is advantageous it becomes more difficult to ensure sufficient strength to react left hand torsional load is achieved through stops dogs 17 with correlatively low axial height. For such applications, it is a further purpose of the present invention to provide means to overcome this limitation by replacing intermediate cam body 14 in tri-cam assembly 10, referring now to FIG. 5A, with intermediate cam assembly 30 acting between drive cam body 12 and driven cam body 13. Intermediate cam assembly 30 is comprised of supplementary stop dog boost ring 31 and intermediate cam tube 32, where dog boost cam pair 33 is provided to act between stop dog ring 31 and intermediate cam tube 32. Dog boost cam pair 33 having boost ramp surfaces 34 and boost catch surfaces 35. In general, intermediate cam assembly 30 acts in the same manner as intermediate cam 14 under application of right and left hand rotation, as already described with reference to FIGS. 4A and 4B for tri-cam assembly 10. Comparing now FIGS. 4B and 5A, the action of stop dog boost ring 31 under application of left hand torque is evident where left hand torque causes stop dog ring 31 to ride up on boost ramp surfaces 34 inducing full engagement of dog stop surfaces 18, such that the engaged height of dog stop surfaces 18 is thus arranged to be greater where the dog boost ring architecture is employed. It will also be apparent that the helix angle of boost ramp surfaces is selected in coordination with the helix angle of dog stop surfaces 18 to induce the indicated full engagement of dog stop surfaces 18 under left hand rotation and similarly the engaged length of boost ramp surfaces 34 are correlatively arranged to have sufficient strength to support the load reacted through dog stop surfaces 18. Referring now to FIG. 5B showing tri-cam assembly 30 under modest right hand rotation, stop dog boost ring 31 is shown fully slid down boost ramp surfaces 34 (cam pair 33 in fully retracted position) as it can be variously induced to move by: prior contact with dog ramp surfaces 19 under right hand rotation (where the helix angle of dog ramp surfaces 19 is selected in coordination with the helix angle of boost catch surfaces 34 to induce such movement); gravity; or a biasing spring (not shown) applying a retracting force relative to intermediate cam tube 32. With respect to this position, cam pair 15 is arranged so that dog stop surfaces 18 have a degree of overlap great enough to ‘catch’ if left hand rotation is applied but ‘clear’ under application of additional right hand rotation causing additional axial stroke under constraint of load thread 20 as illustratively shown in FIG. 5C.

Referring now to FIG. 4C, in certain applications it is desirable to constrain the free axial separation allowed between the drive and driven cam bodies 12 and 13 respectively by providing a latch, particularly to support insertion and removal of fully mechanical gripping tools as described in PCT CA 2006/00710. It is therefore an additional purpose of the present invention to provide a latch operative with the tri-cam architecture supporting latching of drive cam body 12 to driven cam body 13 as illustratively shown in FIG. 6A, where latch 40 is illustrated with tri-cam 10 again in two dimensional representation where the radial planes in which the features of latch 40 occur will in general differ from those in which tri-cam 10 occur. Latch ring 41 is a generally tubular body close fitting with and co-axially mounted on driven cam body 13 having right hand helical slots 42 in which close fitting latch keys 43 are placed where latch keys 43 are rigidly attached to driven cam body 13 which arrangement constrains latch ring 41 to only move between an axially extended and to retracted position relative to driven cam body 13, defining the latch stroke, along a helical path defined by the selected length of helical slots 42 relative to the length of latch keys 43. Latch cam pair 47 is provided to act between latch ring 41 and drive cam body 12 and is defined by generally mating profiled latch hooks 44 having a height selected to be somewhat less than the selected latch stroke, and having back surfaces 45. Latch hooks 44 are shown in their engaged position in FIG. 6A, and thus arranged, prevent axial separation of drive cam body 12 and driven cam body 13 where axial load that might otherwise act to separate is reacted from drive cam body 12 through latch hooks 44 into latch ring 41 and into latch keys 43 as constrained by helical slots 42 and from latch keys 43 into driven cam body 13 to which latch keys 43 are attached. However, upon right hand rotation, referring now to FIG. 6B, latch hooks 44 tend to disengage and latch ring 41 is free to retract as allowed by keys 43 in right hand helical slots 42 where retraction can be variously induced by: gravity; biasing spring 46 acting between latch ring 41 and driven cam body 13; or with sufficient rotation, contact of hook back surfaces 45 with helix angle of mating hook back surfaces 45 selected with respect to helix angle of slots 42 to induce retracting forces. Upon left hand rotation and with cam pair 16 mated as shown in FIG. 6B, i.e., no axial separation, sufficient engagement of latch hooks 44 is yet arranged to re-latch hooks 44. However, if drive cam body 12 is first raised causing axial separation sufficient to prevent engagement of latch hooks 44 then left hand rotation applied, referring now to FIG. 6C, re-latching is prevented and cam pair 16 is active to cause axial stroke.

As illustrated and described with reference to FIGS. 6A through 6C the cam assembly operating procedure, starting in the latched position, can be described in two steps as follows:

1. Set tool down (into work piece) 2. Turn to right (to disengage latch and engage drive cam pair)

Where in order to use the tool to breakout joints by engaging the driven cam pair, two additional steps are required as follows:

3. Pickup on tool 3. Turn to left (to engage driven cam pair)

The operating procedure to disengage the tool from the work-piece is similarly simple and also requires two or three steps from the makeup or breakout ramps respectively, as follows:

1. Set down tool 2. Turn to left (to retract grip assembly and engage latch)

Where in order to latch the tool from the driven cam pair one additional step is required, as follows:

1a. Turn to the right to engage the drive cam pair, then proceed to step 1.

Given the simplicity of the operating procedure, it is possible that an unanticipated or unintentional event could lead to sufficient left hand torque, rotation and compression being applied to the tool simultaneously to engage the latch and that if such events were sufficiently frequent that the risk of unplanned latching and consequently disengagement of the grip assembly from the work piece may be unacceptable. In such applications where it is desirable to constrain the free axial separation allowed between the drive and driven cam bodies, by providing a latch particularly to support insertion and removal of fully mechanical gripping tools, it may also be desirable to prevent unintentional engagement of the latch. To that end, it is a further purpose of the present invention to provide a lockout mechanism operative with tri-cam and latch architecture of FIGS. 4 and 6A through 6C respectively. A further preferred embodiment of the present invention is illustrated in two dimensional schematic views and described with reference to FIGS. 7A through 7F. This embodiment is an integral internal mechanical lockout, design to incorporate lockout function into the cam assembly of FIG. 6A through 6C. The lockout equipped cam assembly operating procedure can be described in six steps as follows:

1. Set tool down (into work-piece) 2. Turn to right (to disengage latch) 3. Pickup (to clear latch hooks) 4. Turn to Left (to engage driven cam pair) 5. Set tool down (to compress spring) 6. Turn to right (to engage lockout, engage drive cam pair, and grip work piece)

Where an additional step is required to breakout joints, as follows:

7. Turn to left (to engage driven cam pair, and grip the work piece)

The operating procedure to disengage the lockout and latch the tool from the makeup position also requires six steps as follows:

1. Set down (to ensure engagement of drive cam pair) 2. Turn to left (to disengage casing and unlock tool) 3. Pickup (to allow latch to spring back) 4. Turn to right (to go back to the drive cam pair) 5. Set down (set down to engage the drive cam pair) 6. Turn to left (to retract the grip assembly and latch tool)

If starting from engagement on the driven cam pair one additional step is required, as follows:

1a. Turn to the right to engage the drive cam pair, then proceed to step 1.

It is evident from the above procedure description that additional steps reduce the risk of unintentional disengagement by increasing operational complexity.

Referring now to FIG. 7A, showing the tri-cam architecture with integral mechanical latch in a schematic two dimensional representation as it would appear with the latch engaged. The tri-cam assembly with lockout has drive cam body 12, driven cam body 13, intermediate cam body 14 and latch 40. Latch cam pair 47 is provided to act between latch body 41 and drive cam body 12 and is defined by generally mating profiled latch hooks 44. Latch hook profile 45 of latch body 41 includes lockout dog 61 on top face 62 and latch hook profile 45 of drive cam body 12 has generally mating lockout dog pocket 63 on bottom face 64 and lockout dog clearance on top face 69. The angles of lockout dog faces 65 and 66 are selected in conjunction with the angle of lockout dog pocket faces 67 and 68, and the geometry of key slots 42 to facilitate engagement of lockout, disengagement of lockout and latch body clearance during makeup. Key slots 42 of latch body 41 and keys 43 rigidly attached to driven cam 13, have lockout face pair 70 comprised of generally mating lockout faces 71 and 72. The angle of lockout faces 71 and 72 is selected in conjunction with the angle of load threads 20 to eliminate unintentional release of lockout due to vibration and to reduce positional uncertainty of lockout dog 61 engagement with toe of latch hook profile 45 of drive cam body 12. Driven cam 13 has stroke limited, pre-stressed compression spring 73, when latch 40 is disengaged biasing spring 46 pushes face 74 latch body 41 into contact with spring stop 75. The spring rate and pre-stress of compressive spring 73 is selected in conjunction with the spring rate and pre-stress of biasing spring 46 such that spring 73 does not compress past the initial pre-stress position under the load of the biasing spring 46 and any incidental loads including component weight.

Referring now to FIG. 7B which shows the cam assembly of FIG. 7A in a schematic two dimensional representation as it would appear with latch disengaged and the latch hook faces in contact, compressive spring 73 remains fully extended and contact with latch body 41 positions it such that the hook faces of latch hook profile 45 are overlapping and slidingly engaged. Keys 43 are positioned in the helical section 77 of key slot 42 such that right hand rotation will cause the latch hook profile to become disengaged and left hand rotation will cause latch body 41 to slide helically on key slots 42 and engage the hook of latch hook profile 45, by extending biasing spring 46 to position the assembly as shown in FIG. 7A.

Referring now to FIG. 7C which illustratively shows the cam assembly of FIG. 7A in a schematic two dimensional representation as it would appear with latch disengaged and under application of left hand torque with helical load ramp surfaces 23 of driven cam pair 16 engaged and helical dog ramp surfaces 19 and mating stop dog surfaces 18 of drive cam pair 15 engaged.

Referring now to FIG. 7D which illustratively shows the cam assembly of FIG. 7A in a schematic two dimensional representation as it would appear under compressive load after engagement on the driven cam pair 16. All mating faces of both drive cam pair 15 and driven cam pair 16 are engaged and cam assembly 10 is under compression. Face 74 of latch body 41 is engaged on spring stop 75 and compressive spring 73 is compressed passed the pre-stress position. Keys 43 are positioned in the helical section 77 of the key slot 42. Lockout dog 61 is engaged in lockout dog pocket 63. application of right hand rotation to the drive cam will move the latch body 41 into the lockout position by bringing the faces 71 and 72 of lockout pair 70 into engagement.

Referring now to FIG. 7E which illustratively shows the cam assembly of FIG. 7A in a schematic two dimensional representation as it would appear with the latch 40 locked out and the drive cam 12 and latch body 41 positioned to disengage the lockout with application with application of left hand rotation relative to the driven cam 13. The toe of latch profile 45 of drive cam 12 is slidingly engaged on face 65 of lockout dog 61, and left hand rotation along the drive cam pitch will result in a similar movement of latch body 41 relative to driven cam 13 and intermediate cam 14, subsequent positive axial movement of the drive cam 12 will cause key 43 to move from lockout section 76 into the helical section 77 of key slot 42.

Referring now to FIG. 7F which illustratively shows the cam assembly of FIG. 7A in a schematic two dimensional representation as it would appear locked out and with right hand rotation applied to the drive cam 12 relative to driven cam 13 and intermediate cam 14. It is understood that, as shown, in the locked out position, both the drive cam pair 15 and the driven cam pair 16 can be active.

It will now be apparent that the integral mechanical lockout architecture of the present invention is well adapted to stop the unintentional latching of the tri-cam architecture of the present invention, due to the reduced likelihood of the additional steps required in the latching sequence occurring unintentionally.

It is understood that the latch can be lockout by a number of means including but not limited to mechanical and hydraulic.

Other arrangements of latching between drive cam body 12 and driven cam body 13 can be similarly provided. One such configuration (not shown) biases latch ring 41 in the normally extended position. Upon right hand rotation latch ring 41 tends to be push latch hooks 44 out of engagement. Latch hooks are shaped and distributed to prevent partial engagement at intermediate rotational positions (within one turn or less) where partial engagement preventing left hand rotation would otherwise occur, as allowed by the pitch of load thread 20 and the selected height of latch hooks 44.

It will now be apparent that the latching tri-cam architecture of the present invention is well adapted to support the provision of additional radial stroke as might be advantageous with externally gripping tools such as shown in FIG. 1, where for example it is typically desirable to grip coupled tubulars having a range of sizes below the coupling.

Internally Gripping (Internal Grip) Tubular Running Tool Tri-Cam Architecture

Referring to FIGS. 8 through 13B, there will now be described a preferred embodiment of an improved gripping tool referred to here as an “internal grip tubular running tool with tri-cam architecture”. Referring now to FIG. 8, showing an external view of the tubular running tool of the preferred embodiment generally designated by the numeral 100 and shown as it would appear in the latched configuration, having body assembly 110, and grip element assembly 120.

Referring now to FIG. 9, showing a cross sectional view of tubular running tool 100 as it would appear in the latched configuration internal to and co-radially located with proximal end 101 of work-piece 102. Tubular running tool 100 is configured at its upper end 105 for connection to a top drive quill, or the distal end of such drive string components as may be attached thereto, (not shown) by load adaptor 112 integral to mandrel 130, so that mandrel 130 acts as the main body of running tool 100. Load adaptor 112 is generally axi-symmetric and made from a suitably strong material. It has an upper end 121 configured with internal threads 122 suitable for sealing connection to a top drive quill, with internal through bore 123 continuous with mandrel 130.

Referring still to FIG. 9, tubular running tool 100 has body assembly 110 comprised of an elongate generally cylindrical mandrel 130 having upper end 131, lower end 132 with external frusto-conical surfaces 133, and internal bore 136. Mandrel 130 has body thread 134 and spline element 135 at upper end 131. Tubular running tool 100 is provided with lock ring 140 having spline section 142 at lower end 141. Lock ring 140 is here shown having generally tubular external sleeve 184 external to and close fitting with load adaptor 112, where external sleeve 184 is provided to protect load adaptor 112 from tong damage. Mandrel 130 carries an internal axially activated grip assembly 120 having an elongate and generally cylindrical lower end 109 inserted and coaxially located within the upper proximal end 101 of a tubular work piece 102. Grip assembly 120 is comprised of cage 144, with upper end 145 and lower end 146, and having thread element 147 at lower end 146, axial retention groove 148, and a plurality of radially oriented windows 149 placed around the circumference at lower end 146, in which jaws 160 are disposed. Generally elongate jaws 160, with upper end 161, lower end 162, inner surface 163 outer grip surface 164 and parallel sides (not shown), have a plurality of frusto-conical contact faces 166 on inner surface 163 that engage with mating frusto-conical surfaces 133 of mandrel 130 forming slip interface 114 acting to provide radial stroke to jaws 160 in response to axial activation.

Referring still to FIG. 9, tubular running tool 100 has bi-rotary to axial stroke activation tri-cam latching linkage 200 generally configured with tri-cam architecture and includes drive cam body 220, driven cam body 260, and intermediate cam body 240. Linkage 200 acts between mandrel 130 and grip assembly 120 and is contained by housing assembly 180 including drive and driven cam housings 181 and 182 respectively. Tri-cam latching linkage 200 functions and is generally arranged as previously described in reference to schematic FIGS. 3 through 4C and 6A through 6C.

Referring now to FIG. 10A, showing linkage 200 in the latched configuration, which assembly is provided with drive cam body 220 having upper end 222. Referring now to FIG. 10B, showing a cross section view of tri-cam assembly 200 in the latched configuration, tri-cam assembly 200 has drive cam body 220 with lower end 223, external surface 224 and internal surface 225, and one or more torque lugs 226 (here shown as eight) at upper end 222. Internal surface 225 of drive cam body 220 has thread element 227 at upper end 222 and seal element 228 at lower end 223. Referring again to FIG. 9, body thread 134 on mandrel 130 threadingly engages thread element 227 on drive cam body 220, while seal element 228 sealingly engages external surface of mandrel 130. Spline section 142 of lock ring 140 meshingly engages both the torque lugs (not visible in this section view, but shown in FIG. 10B referenced with numeral 226) on drive cam body 220 and spline element 135 on mandrel 130 such that drive cam body 220 is structurally and rigidly attached to and prevented from moving both axially and circumferentially relative to mandrel 130. Referring again to FIG. 10B, bottom face 229 of drive cam body 220 contains repeating latch hooks 230. The outside surface 224 of drive cam body 220 contains a plurality of load threads 231 at lower end 223. Load threads 231 are generally comprised of a push thread with load flank 233 and stab flank 234. Drive cam body 220 has seal element 236 on external surface 224 at upper end 222. Referring again to FIG. 10A, drive cam body 220 has dog stop surfaces 232 and dog ramp surfaces 237 located on downward facing shoulder 296 external surface 224 at upper end 222.

Referring still to FIG. 10A, intermediate cam body 240 with upper end 241, lower end 242, inside surface (not shown) and outside surface 244, has one or more dog stop surfaces 245 (shown here as three) at upper end 241 that engage with dog stop surfaces 232 at upper end 222 of drive cam body 220 collectively forming dog stop surface pair 255. Also at upper end 241 of intermediate cam body 240 are one or more (shown as three) dog ramp surface 256 which mate with and slidingly engage dog ramp surface 237 of drive cam body 220 collectively forming dog ramp surface pair 257. Referring again to FIG. 10B, intermediate cam body 240 has load threads 246 (shown here as a multi-start thread form with thread lead matching helix pitch of dog ramp surfaces 256) on inside surface 243 at upper end 241, which threads are arranged as push threads with load flank 247 and stab flank 248, and mate with and slidingly engage load threads 231 of drive cam body 220 forming load thread pair 268, and thus combined with dog stop surface pair 255 and dog ramp surface pair 257 collectively forming drive cam pair 249. Referring now to FIG. 10A, intermediate cam body 240 has one or more (here shown as six) helical load ramp surfaces 250 located adjacent to and co-radial with an equal number stop load surfaces 251 at lower end 242.

Referring still to FIG. 10A, driven cam body 260 with upper end 261, lower end 262, and outside surface 263 has a plurality of helical load ramp surfaces 265 located adjacent to and co-radial with stop load surfaces 266 on upper end 261. Helical load ramp surfaces 265 and stop load surfaces 266 of driven cam body 260 mate with and slidingly engage helical load ramp surfaces 250 and stop load surfaces 251 of intermediate cam body 240 collectively forming driven cam pair 267. Referring now to FIG. 10B, driven cam body 260 has one or more torque lugs 269 in this case twelve (12), on bottom face 270 at lower end 262. Referring now to FIG. 9, torque lugs 269 of driven cam body 260 mate with torque lugs 143 at the upper end 145 of cage 144 and in this embodiment bolted together at bolt holes 297 (bolts not shown) to structurally and rigidly connect driven cam body 260 to cage 144. Referring again to FIG. 10B, on the inside surface 264 at the lower end 262 of driven cam body 260 is seal element 273 and upward facing shoulder 274, while on the outside surface 263 at lower end 262 is seal element 275.

Referring still to FIG. 10B, cam assembly 200 has generally tubular shaped latch ring 300 with upper end 301, lower end 302, and inside surface 303. Referring now to FIG. 11, showing an assembly of drive cam body 220, latch ring 300 and latch keys 290, latch ring 300 has a plurality of helical latch key pockets 305 (here shown as six) which can be evenly spaced circumferentially on outside surface 304. Latch key pockets 305 have inner face 306, load face 307, and helical sliding cam faces 309 and 310. Inner face 306 of latch key pocket 305 has pin clearance slot 308 that extends to inside surface 303 of latch ring 300. Referring again to FIG. 10B, at the lower end 302 of latch ring 300 on the inside surface 303 is upward facing shoulder 315. The top face 312 at the upper end 301 of latch cam 300 has repeating latch hooks 313. Latch hooks 313 on latch cam 300 mates with the latch hooks 230 on the bottom face 229 of drive cam body 220, collectively forming latch hook pair 314, latch hooks 230 and 313 are selected such that when engaged latch hook pair 314 prevents relative axial separation of driven cam body 260 relative to drive cam body 220.

Referring again to FIG. 11A, latch ring 300 is assembled such that latch keys 290 are located internal to latch key pockets 305. Referring now to FIG. 11B, showing a partial cutaway view of a partial cam assembly including driven cam ring 260, latch ring 300, latch pins 337, latch keys 290, and spring elements 346 and 349, latch pins 337 and latch lugs 338 (not shown in this view) are rigidly attached to driven cam body 260 and extend through said cam body to slidingly engage shear pin holes 291 in latch key 290. Referring now to FIG. 10A radially oriented latch pin 337 in combination with radially oriented latch lug 338, which is not aligned in the same radial plane as latch pin 337, collectively restrain movement of latch key 290 relative to driven cam body 260. so that latch ring 300 is constrained to move helically relative to the driven cam body 260 by an amount defined by the relative axial length difference between, referring again to FIG. 11A, the latch key 290 and latch key pocket 305. Referring again to FIG. 11B, latch pin 337 with inside ends 339 extend through clearance slot 308 in latch key pocket 305, and slidingly engage retainer ring pin holes 323 in retainer ring 320 and collectively constrain movement of retainer ring 320 relative to driven cam ring 260. Referring again to FIG. 11A, as assembled load faces 293 of latch key 290 and load face 307 of latch ring 300 collectively form load face pair 315, such that when latched axial load is transferred from the driven cam body 220 (not visible in this view) to the latch ring 300 though load face pair 315. Helical sliding cam faces 296 and 297 of latch key 290 and helical cam faces 309 and 310 of latch ring 300, collectively form helical sliding cam face pairs 317 and 318 respectively, such that when latch keys 290 are moving up or down relative to latch ring 300, cam face pair 318 or 317 respectively is engaged. Referring now to FIG. 11C, showing a partial assembly including drive cam 220, latch ring 300, and latch key 290 as it would appear upon initial right hand rotation of drive cam 220, latch ring 300 tends to be pushed downward to the position shown where hooks 314 still slightly overlap 316 to facilitate re-latching under left hand rotation, as explained with reference to FIG. 6B, but yet not interfere under subsequent right hand rotation causing axial stroke as constrained by movement along load thread 231.

Referring again to FIG. 10B, tri-cam assembly 200 can have spring element 346, in this case a coil spring located internal to latch ring 300 and acting in compression between spring retaining ring 320 and latch ring 300, such that spring element 346 typically works in conjunction with gravity and functions to bias the latch ring 300 in the axial downward position.

Referring again to FIG. 9 tri-cam assembly 200 is located internal to cam housing assembly 180 comprised of driven cam housing 181 rigidly attached to driven cam 260 and sealingly engaged with seal element 275 and drive cam housing 182 rigidly attached drive cam 220 and sealingly engaged with seal element 236, housing assembly 180 provides a sealed cam chamber 183 allowing compressed gas to be added to chamber 183 to function as a spring that will tend to force grip assembly 122 into engagement with work piece 102 upon disengagement of latch 295.

Referring now to FIG. 10A, showing tri-cam assembly 200 in an external view as it would appear in the latched position, where drive cam body 220, driven cam body 260 are at the minimum axial spacing such that drive cam pair (not shown), dog stop surface pair 255 and dog ramp surface pair 257 of drive and intermediate cam bodies 220 and 240 respectively are engaged and driven cam pair 267 of intermediate and driven cam bodies 240 and 260 respectively, are engaged. Referring now to FIG. 10B, showing a cross sectional view of tri-cam assembly 10 in the latched configuration, provided a latch ring 300, which latch 295 is located internal to and co-radially with tri-cam assembly 200 and is described previously in reference to FIGS. 6A through 6C. Latch 295 provides the means to prevent the free axial separation of drive and driven cam bodies 220 and 260 respectively.

Referring now to FIG. 12A, showing an external view of tri-cam assembly 200 as it would appear under application of right hand torque, drive cam pair 249 is engaged and drive cam body 220 has undergone two thirds of a turn relative to driven cam body 260 and intermediate cam body 240. Stop load surface pair 268 and driven cam pair 267 are engaged reacting both axial and torsional load between driven and intermediate cam bodies 260 and 240 respectively. Referring now to FIG. 12B, showing a cross sectional view of tri-cam assembly 200 as it would appear under application of right hand torque as previously described with reference to FIG. 12A. Latch 295 has disengaged and latch ring 300 is in the downward position as biased by gravity (in this orientation) and spring element 346, such that the bottom end 302 of latch ring 300 is engaged on spring element 349. Spring element 349 is a relatively stiff spring, in this case a Belleville washer stack comprised of three Belleville washers arranged in parallel and preloaded in compression such that the combined force of the biasing elements acting on latch ring 300 are small relative to the preload of spring element 349 and as such the position of spring element 349 is known and consequently the axial position of the downward biased latch ring 300 is also known. Spring element 349 functions to prevent overload of latch hooks 314 in the event that compressive load is applied to tri-cam assembly 200 with only limited latch hook pair 314 engagement. Left hand helical drive cam pair 255, in this case is six start American buttress push thread form, allows rotation causing axial stroke in excess of one full rotation which is greater than would be possible with single bi-rotary cam pair as described with reference to FIGS. 2A and 2B.

Referring now to FIG. 13A, showing an external view of tri-cam assembly 200 as it would appear with latch 295 disengaged and under application of left hand torque, driven cam pair 267 is engaged and drive and intermediate cam bodies 220 and 240 respectively have undergone a relatively small amount of rotation with respect to driven cam body 260. Dog stop surface pair 255 and helical dog ramp surface pair 257 have engaged to react axial and torsional load between drive cam body 220 and intermediate cam body 240. Referring now to FIG. 13B, showing a cross sectional view of tri-cam assembly 200 as it would appear with latch 295 disengaged and under application of left hand torque, latch ring 300 is in the downward position such that bottom end 302 of latch ring 300 is in contact with spring element 349. To move tri-cam assembly 200 from the latched configuration as previously described with reference to FIGS. 9A and 9B to the configuration shown in FIGS. 13A and 12B right hand torque needs to first be applied to disengage latch 295 then axial displacement is applied sufficient to move latch hooks 314 out of range of overlap (see FIG. 11B) such that under applied left hand torque, driven cam pair 267 will engage without interference of the latch hooks 314. Referring again to FIG. 9, the axial stroke required to move latch hooks 314 out of range of engagement is arranged to fall within the dead stroke of the tool, i.e., the axial stroke required before possible engagement of grip assembly 120 on work-piece 102. Right hand helical driven cam pair 267, in this case a six start ramp provides axial stroke and torsion load under left hand rotation at an intermediate cam angle and also provides free axial separation of intermediate and driven cam bodies 240 and 260 respectively if latch 295 is disengaged, allowing axial stroke of gripping tool 100 to act to grip work piece 102 under action of applied axial load independent of rotation.

In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the Claims. 

1. An improvement in a gripping tool having a grip surface carried by movable grip elements and linkages to radially move the grip surface from a retracted to an extended position, the improvement comprising: the linkages containing at least one tri-cam linkage, comprising: a drive cam body which receives rotational input tending to urge rotational movement, an intermediate cam body which receives rotational input solely from the drive cam body; a driven cam body which receives rotational input solely from the intermediate cam body; a drive cam pair acting between the drive cam body and intermediate cam body, such that rotational input is transmitted by the drive cam pair from the drive cam body to the intermediate cam body, and a driven cam pair acting between the intermediate cam body and driven cam body, such that rotational input from the intermediate cam body is transmitted by the driven cam pair to the driven cam body.
 2. The improvement of claim 1, wherein the tri-cam linkage supports bi-rotary to axial stroke activation and radial stroke of the grip surface as a function of axial stroke.
 3. The improvement of claim 2, wherein the drive cam pair is arranged to only be active to cause axial stroke as a function of rotation under a first direction of rotation and the driven cam pair under a second direction of rotation, which separation of bi-rotary activation into two cam pairs facilitates providing greater axial stroke and correlatively radial stroke of the grip surface than is possible where a single cam pair is employed in a bi-rotary activated linkage.
 4. The improvement of claim 1, wherein the tri-cam linkage is arranged with a latch that when engaged will prevent axial stroke activation of the tri-cam linkage.
 5. The improvement of claim 4, wherein the tri-cam linkage is provided with a mechanical lockout that when activated prevents engagement of the latch.
 6. The improvement of claim 1 wherein the gripping tool has a load adaptor and the at least one tri-cam linkage arranged such that: the drive cam body is rigidly secured to and receives rotational input from the load adaptor tending to urge rotational movement.
 7. The improvement of claim 6, wherein the tri-cam linkage supports bi-rotary to axial stroke activation and radial stroke of the grip surface as a function of axial stroke.
 8. The improvement of claim 6, wherein the drive cam pair is arranged to only be active to cause axial stroke as a function of rotation under a first direction of rotation and the driven cam pair under a second direction of rotation, which separation of bi-rotary activation into two cam pairs facilitates providing greater axial stroke and correlatively radial stroke of the grip surface than is possible where a single cam pair is employed in a bi-rotary activated linkage.
 9. The improvement of claim 6, wherein the tri-cam linkage is arranged with a latch that when engaged will prevent axial stroke activation of the tricam linkage.
 10. The improvement of claim 9, wherein the tri-cam linkage is provided with a mechanical lockout that when activated prevents engagement of the latch. 